[mythtv] Packagers: use system libudfread if available

[David Hampton]

On Sun, 2021-11-07 at 01:16 -0400, Scott Theisen wrote:
> Hello all,
> 
> See https://github.com/MythTV/mythtv/pull/411

Looks good.

> Anyone know if libudfread is packaged with/as a part of libbluray on 
> some systems?

I have the libblurary package installed on my freebsd and mac builders.
Neither has a libudfread.{a,so} file installed, nor do they have
packages to install them.

David